Telecom Professional Qualification flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

OSI seven layers

Physical, Data Link, Network, Transport, Session, Presentation, Application. Each layer serves the one above it and adds its own header or framing information.

Shannon capacity formula

C = B·log2(1 + S/N), giving the maximum error-free bit rate over a noisy channel of bandwidth B hertz at signal-to-noise ratio S/N.

Circuit versus packet switching

Circuit switching reserves a dedicated end-to-end path for the whole session. Packet switching shares links statistically, adding headers and queuing but suiting bursty data traffic.

STM-1 line rate

Synchronous Digital Hierarchy first level runs at 155.52 Mbit/s. Higher levels multiply by four: STM-4 is 622.08 Mbit/s and STM-16 is 2.488 Gbit/s.

PCM voice channel rate

Sampling at 8 kHz with 8-bit companding yields 64 kbit/s per voice channel. Thirty-two such channels, including framing and signaling, form a 2.048 Mbit/s E1.

OTN frame layers

The optical transport network wraps client signals in an OPU payload unit, adds ODU overhead for management and tandem connection monitoring, then OTU framing with forward error correction.

Subnet usable host count

For an IPv4 prefix length p, usable hosts equal 2^(32−p) minus 2, one address for the network and one for broadcast. A /24 therefore supports 254 hosts.

BGP path selection order

Cisco-style order: highest weight, highest local preference, locally originated, shortest AS path, lowest origin type, lowest MED, then eBGP before iBGP.

DHCP DORA exchange

Client broadcasts Discover, server replies Offer, client sends Request for a specific offer, server confirms with Acknowledge. Renewal normally starts at half the lease duration.

LTE duplex and multiple access

LTE uses OFDMA on the downlink and single-carrier FDMA on the uplink to reduce peak-to-average power ratio. Channel bandwidths range from 1.4 to 20 MHz.

5G NR subcarrier spacing

Subcarrier spacing equals 15 kHz multiplied by 2^μ, giving 15, 30, 60, or 120 kHz. Wider spacing shortens symbols and suits millimeter-wave bands.

2.4 GHz non-overlapping channels

In IEEE 802.11 at 2.4 GHz only channels 1, 6, and 11 do not overlap in most regulatory domains, because each channel is about 20 MHz wide.

GPON rates and wavelengths

Gigabit PON carries 2.488 Gbit/s downstream at 1490 nm and 1.244 Gbit/s upstream at 1310 nm, with 1550 nm optionally reserved for video overlay.

XGS-PON characteristics

XGS-PON provides symmetric 10 Gbit/s capacity, transmitting upstream near 1270 nm and downstream near 1577 nm so it can coexist with legacy GPON on the same fiber.

VDSL2 vectoring purpose

Vectoring coordinates signals across copper pairs in a binder to cancel far-end crosstalk, letting VDSL2 profiles such as 17a and 35b reach higher bit rates over short loops.

ITU radio regions

The ITU Radio Regulations divide the world into three regions: Region 1 Europe, Africa and the Middle East; Region 2 the Americas; Region 3 Asia-Pacific. Allocations differ by region.

Spectrum auction formats

Simultaneous multiple-round ascending auctions let bidders compete for packages of licenses over rounds. Alternatives include beauty contests, comparative selection, and administrative assignment.

Class licence meaning

A class or general authorization permits anyone meeting published technical conditions, such as power and emission limits, to operate without an individual site-specific licence.

IPsec ESP versus AH

Encapsulating Security Payload encrypts and authenticates packet contents. Authentication Header provides integrity and origin authentication only, without confidentiality. IKE negotiates both.

Availability from MTBF

Availability equals MTBF divided by the sum of MTBF and MTTR. Five nines, or 99.999 percent, allows roughly 5.26 minutes of downtime per year.

AAA functions

Authentication verifies identity, authorization grants permissions or attributes, and accounting records usage. RADIUS and Diameter carry these exchanges for dial, broadband, and mobile access.

SDN control plane separation

Software-defined networking moves forwarding decisions to a centralized controller and leaves devices as data-plane forwarders, programmed through southbound interfaces such as OpenFlow.

NFV MANO components

Management and orchestration comprises the NFV orchestrator for service lifecycle, the VNF manager for virtual function instances, and the virtualized infrastructure manager for resources.

MQTT versus CoAP

MQTT is a lightweight publish-subscribe protocol over TCP with a broker. CoAP is a REST-style request-response protocol over UDP, suited to constrained devices and lossy networks.

Network slicing definition

A slice is an isolated logical network on shared infrastructure with its own resources, configuration, and service-level agreement, tailored to a use case such as industrial control.

ARPU calculation

Average revenue per user equals total service revenue divided by the average number of subscribers in the period. It is usually reported monthly and compared across segments.

CAPEX versus OPEX

Capital expenditure covers assets such as network equipment and fiber, depreciated over years. Operating expenditure covers ongoing costs such as maintenance, power, rent, and licenses.

Subscriber churn rate

Churn is the percentage of subscribers who leave during a period, calculated as disconnections divided by the average subscriber base. Lower churn improves lifetime value.

MOS voice quality scale

Mean opinion score rates perceived voice quality from 1 (bad) to 5 (excellent). Scores above about 4.0 are usually considered toll quality for planning purposes.

ITU-T G.114 latency limit

G.114 recommends one-way voice latency below 150 milliseconds for most applications. Above roughly 400 milliseconds, conversational quality degrades noticeably even without packet loss.

Standards body roles

ITU-T defines telecom protocols, ITU-R manages radio spectrum, 3GPP develops cellular specifications, IEEE covers local networks, and the IETF publishes Internet RFCs.

DSCP per-hop behavior

The six-bit differentiated services code point in the IP header selects a per-hop behavior such as expedited forwarding for voice or assured forwarding classes for data.